package com.lbc.pc;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

/**
 *  线程之间的通信问题
 *  线程交替执行  a b  操作同一个变量  num = 0
 *  a  num+1
 *  b  num-1
 */
public class B {
    public static void main(String[] args) {
        Data2 data = new Data2();

        new Thread(()->{
            for (int i = 0; i < 20; i++) {
                try {
                    data.increment();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "A").start();

        new Thread(()->{
            for (int i = 0; i < 20; i++) {
                try {
                    data.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "B").start();

        new Thread(()->{
            for (int i = 0; i < 20; i++) {
                try {
                    data.increment();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "C").start();

        new Thread(()->{
            for (int i = 0; i < 20; i++) {
                try {
                    data.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }, "D").start();
    }
}

//  等待，业务，通知
class Data2 {  //  属性、方法

    private int number = 0;

    Lock lock = new ReentrantLock();
    Condition condition = lock.newCondition();

    //  + 1
    public void increment() throws InterruptedException {
        lock.lock();
        try {
            //  业务代码
            while (number!=0) {
                //  等待
                condition.await();
            }
            number++;
            System.out.println(Thread.currentThread().getName()+"==>"+number);
            //  通知其他线程，我+1完毕了
            condition.signalAll();  //  唤醒全部
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }

    }

    //  - 1
    public void decrement() throws InterruptedException {
        lock.lock();
        try {
            while (number==0) {
                //  等待
                condition.await();
            }
            number--;
            System.out.println(Thread.currentThread().getName()+"==>"+number);
            //  通知其他线程，我-1完毕了
            condition.signalAll();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

}
